1. Field of the Invention
The present invention relates to hangers or support racks used for supporting articles in electrically conductive contact during transport through an electrostatic finishing station. In particular, the present invention relates to support racks having universally adjustable support hooks.
2. Discussion of Background
In the powder painting industry, articles are supported on hangers and carried along by a conveyor through a finishing station, which may include the steps of cleaning, rinsing, drying, coating and baking. Usually finishing includes traveling through an electrostatic spray booth where the articles, electrostatically grounded through the hanger to the conveyor, are coated with an electrically charged paint particulate. After the articles have been coated with the paint particulate, the hangers are transported to an oven where the paint is baked onto each article.
Each painting and baking operation, in addition to applying paint to the articles, applies a coating to the exposed portions of the hanger as well as the hooks, except for a small area where the hooks contact the articles. Unless similar articles are painted in subsequent operations, where each article would be in electrical contact with the hook in the same location, it is necessary to provide a clean support hook for each subsequent operation. In addition, because the hanger is coated each time it travels through the finishing process, the electrical contact between the hooks and the hangers can become covered and damaged, thus requiring the hanger to be cleaned before using it in another coating process.
When the hooks and hangers become coated with a baked paint, the coating cannot be merely washed away or cleaned but must be either burned off or chipped away. During the baking process the articles are subjected to temperatures between approximately 300.degree. F. and 400.degree. F., but in order to burn the paint off, the hangers and hooks must be subjected to temperatures over 1000.degree. F., which obviously consumes a large amount of energy. Therefore, it is important that the hangers be able to be used as many times as possible before having to be cleaned.
It is not practical to chip away the paint from the hanger, thus the paint must be burned away; however, with regard to the hooks, the paint can be chipped away. By tumbling the hooks together with stones, rocks, or some other tumblers, the paint will chip away. This is a practical and economical solution for the hooks, but it is not practical for the hangers. Consequently, it is important to provide a hanger system that optimizes the number of cycles the hanger can undergo before cleaning is necessary.
It is also important in electrostatic painting operations that the articles be in good electrical connection with the hooks and that the hooks be in good electrical connection with the hanger. In addition, because there are a variety of sizes and shapes of articles to be painted, it is important that the hanger and hooks be able to be adapted or modified to support the various articles. In other words, each hanger must have flexibility regarding the size and shape of article to be supported, otherwise the number of dedicated hangers would be enormous.
Consequently, there is a need for a hanger system that will provide flexibility and which will assure good electrical contact between the articles and hooks and, more importantly, the hooks and hangers. In addition, there is a need for a hanger system having the previous described features, but also a system which can be used numerous times or cycles without having to be cleaned.